Perhaps to most animals things are simply as they find them, but for most humans there’s a theory for everything that exists and even for what ought to exist. If we believe a world under one government would be good for mankind we can devise a theory of how to achieve it, perhaps region by region initially. However, any government must depend, eventually, on the consent of the people.
North America (NAFTA), South East Asia (ASEAN), Africa (EAC), Europe (EU), … maybe we are already progressing down the road towards world government.  It is an idea that has widely held, if generally superficial, appeal; we find it in popular songs such as John Lennon’s ‘Imagine’: “Imagine there’s no countries … Nothing to kill or die for … Imagine all the people, Living life in peace … Imagine all the people, Sharing all the world … And the world will live as one” – it is regarded by many as his greatest song (“People say I’m a dreamer, But I’m not the only one“).
World government was what Jean Monnet believed would prevent further world wars, an idea shared by his friend Harold Macmillan and then Foreign Secretary, Edward Heath, later the Prime Minister who took Britain into the Common Market. Since Europe had managed to trigger successive global wars they wanted to end nation states in the fractious continent, and ultimately everywhere. Confederations like the Council of Europe or EFTA–sovereign nations working together under treaty for a common purpose–were, to them, insufficient.
We can see why ‘confederacy’ might not seem good enough by such leaders. Take the UN for example, it’s easy to think it’s a bit toothless despite its blue beret soldiers having played a vital role in many conflicts. However, the General Assembly can muster lots of votes against British colonialism for defending the right of Falkland islanders to resist Argentinian control; Gibraltarians too could lose the association with Britain that they have voted to retain if the Assembly decided for them. On the other hand the Security Council will stymie practically anything that should be done to protect Tibetans, Uighers, etc.
Imagine if the UN had an agenda like the EU, to accrete powers until it governed all its members. The General Assembly would become a global parliament with a senate, president and all the requisites of government too. It’s doubtful that would ensure fair and democratic rule or that world peace would follow.
The EU is currently between confederation and federation but on a path to the latter. We now know from papers released under the 30-year rule that the three amigos (Monnet, Macmillan and Heath) discussed the plan for a federal union, a United States of Europe, before Macmillan applied for UK entry to the Common Market, but the implications for loss of sovereignty were deliberately hidden from the public for fear that voters wouldn’t stomach it.  No matter, De Gaulle vetoed the bid.
Heath repeated the deception after the UK’s third application was accepted. From Heath’s broadcast to mark UK entry to the EEC, January 1973: “there are some in this country who fear that in going into Europe we shall in some way sacrifice independence and sovereignty. These fears, I need hardly say, are completely unjustified.”
Wilson’s 1975 referendum pamphlet stated, “No important new policy can be decided in Brussels or anywhere else without the consent of a British Minister answerable to a British Government and British Parliament.” That was only true until majority voting (QMV) was introduced by the Lisbon Treaty, signed by Gordon Brown without the referendum promised in Labour’s election manifesto.
John Major enabled the big step from trading agreement (Common Market) to federation (EU) by signing the Maastricht Treaty, again without asking voters. Tony Blair assured us when he signed the Charter of Fundamental Rights that it was no more justiciable than the Beano, but it’s the CJEU that decides whether a terrorist can be deported.
World government may be idealistic but to most people it is also an illusion, for the foreseeable future anyway. Maybe Xi Jinping and Vladimir Putin have similar ideas–regional or global ambitions are not necessarily beneficent or peaceful.
On the day of the Brexit referendum, in a poll of over twelve thousand voters, half of those who voted to leave the EU said sovereignty was the biggest single reason for their choice. A third put control of immigration as their top reason and a mere 6% put the economy first–which shows that the Remain campaign missed the target, it didn’t understand the public’s concerns (and most of the public probably felt they didn’t understand the economics either). 
Supranational government requires democratic consent if it is to benefit ‘the people’ and not just the rulers and influencers. Power must be revocable because even idealists can become convinced of their infallibility–that seems to be the usual pattern for leaders who cannot be challenged by a ballot.
Our title of course comes from another song about world union, admittedly a play on rugby union and how international sport can help bring harmony between nations (like when the English test cricket team are welcomed by the Australians?)